This invention generally relates to endoscopic instruments. More particularly, the present invention provides a ratcheting mechanism to rotationally adjust an endoscopic instrument.
Laparoscopic, endoscopic, and other minimally invasive surgical techniques enable surgeons to perform fairly complicated procedures through relatively small entry points in the body. The term xe2x80x9claparoscopicxe2x80x9d refers to surgical procedures performed on the interior of the abdomen, while the term xe2x80x9cendoscopicxe2x80x9d refers more generally to procedures performed in any portion of the body. Endoscopic surgery involves the use of an endoscope, which is an instrument permitting the visual inspection and magnification of a body cavity. The endoscope is inserted into a body cavity through a cannula extending through a hole in the soft tissue protecting the body cavity. The hole is made with a trocar, which includes a cutting instrument slidably and removably disposed within a trocar cannula. After forming the hole, the cutting instrument can be withdrawn from the trocar cannula. A surgeon can then perform diagnostic and/or therapeutic procedures at the surgical site with the aid of specialized medical instruments adapted to fit through the trocar cannula. Additional trocar cannulas may provide openings into the desired body cavity.
Some known advantages of minimally invasive surgical techniques include reduced trauma to the patient, reduced likelihood of infection at the surgical site, and lower overall medical costs. Accordingly, minimally invasive surgical techniques are being applied to an increasingly wider array of medical procedures.
FIG. 1 depicts a typical example of an endoscopic instrument 100. The instrument 100 may include a handle 110, a knob 120, and a tubular member 130. The handle 110 may be one of a variety of conventional configurations, such as a grip handle shown in FIG. 1. A portion of the handle 110 fits within a proximal end of the knob 120, providing an axis about which the knob 120 can be rotated. A distal end of the knob 120 may engage the proximal end of the tubular member 130, such that any rotation of the knob 120 may cause the tubular member 130 to rotate as well. The distal end of the tubular member 130 may include one of a variety of instruments or so-called end effectors. For example, the distal end may be equipped with jaws, cutting blades, or some other instrument, depending on the desired use of the endoscopic instrument.
It is often useful for a practitioner of endoscopic surgery to rotationally manipulate the distal end of the tubular member 130 while firmly grasping the handle 110 in a comfortable manner, thus allowing the distal end of the tubular member to rotate relative to the handle. Additionally, it is often useful to incrementally rotate the distal end of the tubular member 130 by some predetermined angular displacement so that the practitioner may visualize the rotation relative to the handle 110.
FIG. 2 depicts a cross section of a knob 120 having a conventional ball and spring detent mechanism. Within the knob 120 is a cylindrical drum 205 having a plurality of detents 210. Typically, a channel 215 may extend partially through the knob 120, the channel 215 being oriented radially with respect to the cylindrical drum 205. The ball and spring mechanism is positioned within the channel 215. As the name implies, a compression spring 220 is used to hold a ball 225 in contact with the cylindrical drum 205. To prevent the ball and spring mechanism from falling out of the knob 120, a set screw 230 may be used to seal the channel 215. The set screw 230 may also be used to adjust the amount of compression force that is applied to the spring 220. The ball, spring, and set screw may be separate components or may be integrated into a single component, as is known to the art. The portion of the handle that fits within the knob may engage the cylindrical drum 205, or the cylindrical drum 205 may be an integral part of the handle.
As the knob 120 is rotated with respect to the handle, the ball 225 travels around the circumference of the cylindrical drum 205. When the ball 225 is aligned opposite to one of the detents 210, the spring 220 pushes the ball 225 into the detent 210. If additional rotational force is applied to the knob 120, then the ball 225 is removed from the detent 210. The amount of force needed to remove the ball 225 from the detent 210 depends on a number of factors, including the shape and depth of the detent 210, the shape and size of the ball 225, and the amount of compression force applied by the spring 220 and/or set screw 230. The spring 220 is conventionally made of metal to provide sufficient compressive force. The movement of the ball 225 into and out of the detents 210 provides tactile feedback to the user.
While the ball and spring detent mechanism design approach is functional, it requires several components and assembly processes to assure instrument reliability. Even so, these devices often fail over time as the metal components corrode causing the mechanism to jam.
Accordingly, there is a need to provide an incremental rotational displacement mechanism for use with endoscopic instruments that is resistant to corrosion failure and that may be easily assembled.
In accordance with the present invention, there is an endoscopic instrument having a circular detent housing coupled to a first end of a knob. The circular detent housing has a plurality of detents arranged along the perimeter of the detent housing. A tubular member fixedly engages a second end of the knob. A detent ring is positioned coplanar to and within the perimeter of the detent housing. The detent ring has at least one detent arm and at least a portion of the at least one detent arm engages at least a portion of the detent housing. A handle is coupled to the detent ring.
In accordance with another aspect of the invention, there is an incremental rotational displacement mechanism. The mechanism includes a circular detent housing, a detent ring, and a handle. The detent housing has a plurality of detents arranged along the circumference of the detent housing. The detent ring has at least one detent arm and is positioned coplanar to and within the circumference of the detent housing, such that at least a portion of the at least one detent arm engages at least a portion of the detent housing. The handle engaging the detent ring such that a force applied to the handle causes the detent ring to rotate with respect to the circular detent housing.
In accordance with yet another aspect of the invention, the circular detent housing is formed within the first end of the knob.
In accordance with still another aspect of the invention, the detent ring has at least two arms. The two arms may have the same length or have different lengths.
In accordance with another aspect of the invention, the plurality of detents are arranged at either regular or irregular intervals along the perimeter of the detent housing.
It should be emphasized that the term xe2x80x9ccomprisesxe2x80x9d or xe2x80x9ccomprising,xe2x80x9d when used in this specification, is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof